Composite selector switch and reversing switch for tap-changing regulating transformers

ABSTRACT

A selector switch and a reversing switch for tap-changing regulating transformers are integrated into a unitary structure performing both the function of tap-selection in connection with a tapped transformer winding and of reversing the terminals of a tapped transformer winding. This integral dual function switch is very compact, hardly exceeding the bulk of a conventional selector switch without reverse switching means.

United gtates Patent lnventors Alexander Bleihtreu; Josef A. Kreazpaintner, 120th of Regensburg, Germany Appl. No. 856345 Filed Sept. 9, W69 Patented June 29, 1971 Assignee Maschinenfalzrik Reinhausen Gebrucler Schentreck K. G. Regensburg, Germany Priority Sept. 14, 1968 Germany P 17 88 013.6

COMPOSITE SELECTOR SWITCH AND REVERSING SWITCH FOR TAP-CHANGING REGULATING TRANSFORMERS 7 Claims, 7 Drawing Figs.

11.8. C1 200/11, 323/435 lnt. Cl H01h19/58. H01h 21/78 Field of Search 200/11, 14; 323/435 56] References Cited UNITED STATES PATENTS 3,176,089 3/1965 Bleibtreu et a1. 200/11 TC 3,233,049 2/1966 Bleibtreu 200/11 TC 3,250,864 5/1966 Bleibtreu et al. 200/11 TC 3366750 1/1968 Bleibtreu 200/11 TC 3,366,763 1/1968 Bleibtreu et al. 200/11 TC Primary Examiner-J. R. Scott AttorneyErwin Salzer ABSTRACT: A selector switch and a reversing switch for tapchanging regulating transformers are integrated into a unitary structure performing both the function of tap-selection in connection with a tapped transformer winding and of reversing the terminals of a tapped transformer winding. This integral dual function switch is very compact, hardly exceeding the bulk of a conventional selector switch without reverse switching means.

COMPOSITE SELECTOR SWITCH AND REVERSING SWITCH FOR TAP-CHANGING REGULATING TRANSFORMERS BACKGROUND OF INVENTION Tap-changing regulating transformers frequently include three basic units, i.e. a transformer having a tapped winding, a selector switch, and a transfer switch. Selector switches are provided to select the desired tap on a tapped transformer winding, and transfer switches for inserting the desired tap into a circuit. Selector switches do not perform any switching operations between contacts that carry currents. This task is performed by the transfer switches. Some tap-changing regulating transformers include, in addition to selector switches and transfer switches, reversing switches. The function of reversing switches is to change the polarity of the terminals of a tapped transformer winding. Thus, depending upon the position of the reversing switch, the voltage generated in a particular portion of a tapped transformer winding may be used either to boost, or to buck, another voltage and more particularly the voltage generated in a transformer winding which is not tapped, or principal transformer winding.

This invention relates generally to a tap-changing regulating transformer including selector switch means, transfer switch means and reversing switch means, i.e. systems of the kind described in considerable detail in US. Pat. No. 3,366,763 to A. Bleibtreu et al., .Ian. 30, 1968 for Reversing Switch for Tap- Changing Regulating Transformers to which reference may be had for certain details not disclosed below having a bearing on the present invention, but not directly involved in the same.

This invention is more particularly related to a novel unit which includes both the selector switch means and the reversing switch means, and whose outstanding feature consists in great compactness, thus making it possible to greatly reduce the bulk of a tap-changing regulating transformer.

The structure according to the present invention is an adaptation of multipolar rotary selector switches as disclosed in US. Pat. No. 3,233,049 to A. Bleibtreu, Feb. 1, 1966 for Integral Selector Switch and Transfer Switch Unit for Tapped Regulating Transformers; in U.S. Pat. No. 3,250,864 to A. Bleibtreu et al., May 10, 1966, for Regulating Transformers Having a Large Number of Taps, and in US. Pat. No. 3,366,750 to A. Bleibtreu, Jan. 30, 1968 for Switching Mechanism for Tapped Regulating Transformers.

SUMMARY OF INVENTION A combined selector switch and reversing switch embodying this invention includes a first plurality of fixed contacts arranged to form a first circular pattern, the constituent contacts of said first plurality of contacts having a relatively small circular pitch at one side of said circular pattern and a relatively large circular pitch at the opposite side of said circular pattern. A first contact arm is pivotable about the center of said first circular pattern and has a radially outer end selectively engageable with each of said first plurality of fixed contacts. The switch further includes a second plurality of fixed contacts arranged to fonn a second circular pattern in coaxial relation to said fust circular pattern. The constituent contacts of said second plurality of contacts have a relatively small circular pitch on one side of said circular pattern and a relatively large circular pitch at the opposite side of said circular pattern. The region of said second circular pattern where there is a relatively large circular pitch between the constituent contacts thereof includes a center contact. The switch further includes a pair of additional fixed contacts immediately adjacent said center contact each having the same angular pitch relative to said center contact and each fonning part of said second circular pattern. A second contact arm is pivotable about the center of said second circular pattern and has a radially outer end selectively engageable with each of said second plurality of fixed contacts. The structure further includes a movable reversing contact pivotable about the center of said second circular pattern and selectively conductively connecting said center contact with one of additional fixed contacts.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows in vertical section a combined selector switch and reversing switch embodying this invention, FIG. 1 being a section taken substantially along II of FIG. 2;

FIG. 2 is a transverse section of the structure shown in FIG. 1 taken substantially along the line II-Il of FIG. 1;

FIG. 3 is a development of the contact structure of FIGS. 1 and 2 into a plane, i.e. the plane of the paper on which FIG. 3 is drawn;

FIG. 4 is a diagrammatic representation of the circuitry of the structure of FIGS. 1 and 2;

FIG. 5 is a section substantially along l-l of FIG. 2 and shows on a larger scale than FIG. 1 the above referred-tocenter contact and its associated parts;

FIG. 6 shows on a larger scale than FIG. 1 a portion of the drive mechanism shown in FIG. 1 for the combined selector and reversing switch; and

FIG. 7 is a top plan view of the structure shown in FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawings, and more particularly to FIGS. 1 and 2 thereof, a plurality of vertical bars 21 of insulating material are arranged to define a cylindrical surface and form a squirrel-cagelike structure for supporting the fixed contacts of a composite selector and reversing switch. The selector and reversing switch of FIGS. 1 and 2 is intended to be used together with three tapped transformer windings each having thirteen taps. Each tap is conductively connected to a fixed contact supported by vertical insulating bars 21. The 13 fixed contacts of each of the three phases may be designated by the reference characters 1,2,3,4,5.....8,9,l0,1l,12,13. Assuming that each of the three tapped windings of the transformer is associated with one phase U,V,W of a three phase electric system, then the fixed odd contacts of the three phases of the selector and reversing switch are arranged in three parallel planes, or layers, U ,,W, and the fixed even contacts of the three phases of the selector switch are arranged in three parallel planes, or layers, U V,, W,. Contacts l,2,3,4,5....8, 9,10,11,12,]3 are substantially in the shape of short studs projecting transversely through vertical insulating bars 21. FIG. 1 shows to the left thereof a vertical insulating bar 21 supporting the fixed contacts 5 and 6 of all three phases U,V,W. The lower ends of insulating bars 21 are tied together and supported by a frame structure 22, and the upper ends of bars 21 are held in position by like means as, for instance, a disc. As clearly shown in FIG. 3 each insulating bar 21 supports an even fixed contact and an odd fixed contact for each phase U,V,W. Thus, considering bars 21 from left to right, the first bar 21 supports the fixed contacts 5,6 of each phase U,V,W or a total of six fixed contacts, the second bar 21 supports the fixed contacts 3, 4 of each phase U,V,W, or a total of six contacts, etc. Fig. 3 further clearly illustrates that the fixed even contacts 2,4,6...8,10,12 and the fixed odd contacts l,3,5....7,9,11,l3 are arranged in planes parallel to each other. Reference numeral 27 has been applied to indicate a center column arranged in coaxial relation to the squirrel-cage structure formed by insulating bars 21. Column 27 supports a plurality of pairs of stationary slip rings 25,26 mounted on the outer surface thereof. The structure of FIGS. 1 and 2 further includes contact arms or contact bridges 23 and 24 of which each is pivotable about the longitudinal axis of column 27. When pivoted, the radially inner ends of contact arms or contact bridges 23 slide on the surfaces of slip rings 25, while the radially outer ends of contact bridges 23 are adapted to engage selectively the odd numbered fixed contacts 1,3,5....9,11,l3 of the three phases U,V,W. When contact bridges 24 are pivoted their radially inner ends slide upon the surfaces of slip rings 26, while the radially outer ends of contact bridges24 are adapted to engage selectively the even numbered fixed contacts 2,4,6 ...8.l0,l2 of the three phases U,V;W. In FIG. I. but the three bridges 24 can be seen, the

three contact bridges 23 having been sectioned away. FIG. 2

pitch or spacing between adjacent insulating bars 21, or the angular relation between adjacent insulating bars 21 is not equal and corresponds to the difference in potential between the fixed contacts supported by the insulating bars 21. To be more specific, the spacing between, or the angles enclosed between, the insulating bars supporting contacts 1 and 3 and 5 and 7 and 9 and 11 is smaller thanthe angular pitch or spacing between, or the angles enclosed between, the insulating bars 21 supporting contacts 11 and I3, and I3 and 1, respectively. This is particularly evident from FIG. 3. y

The insulating bar 21 at the extreme right of FIGS. I and 2 supports fixed center contacts K arranged at the levels uni t..yrtcinnrn tnrhsndd .n nhrrssiflrrisqnnsn l,3,5...9.11,l3 of the switch. Fixed center contacts K are adapted to be engaged by the radially outer ends of contact arms or contact bridges 24. The spacing between. or the angles enclosed by the insulating bars 21 supporting even numbered fixed contacts 2,4; and 4.6; and 6.8; and 8,10; and 10,12

is less than the spacing between, or the angles enclosed .tixed reversingswitch contacts to which reference characters and have been applied. Contacts are intended to be permanently connected by leads to opposite ends of a tapped transformer winding. Reversing switch contacts and are arranged in the same cylindrical surface as fixed contacts 1 to 13 of phases U,V.W and vertical insulating rods 28.29 form part of the squirrel cage structure defined by vertical insular ing rods 21.

The three fixed contacts K are arranged in the planes or at the levels Ug,V;.W; and. adapted to be engaged by the radially outer ends of contact bridg s 24. Each center contact K is provided with a terminal or connector 51 for connecting the same to a nontappcd or principal transformer winding, as will be shown below more in detail in connection with FIG. 4.

Reference numeral .30 has been applied to indicate three sector=shapcd movable reversing switch contacts. The movable reversing switch contacts are pivotable about the common longitudinal axis of column 27 and the squirrel cage structure formed by vertical bars 21. Thus contact 30 may be used to selectively conductiv ly connect fixed reversing switch contacts =land-contacts K. or fixed reversing switch contacts and contacts K. The movable reversing switch contacts 39 are affixed to scgmcnt shaped contact supports 31. The latter are tied together by vertical tie rods 32 of insulating material. The upper ends of tie rods 32 are affixed to an arm 34 having a radially inner bearing 36 pivotslly mounted on th outer surface of switch column 27. In like fashion the lower ends of tie rods 32 are affixed to an arm having a radially inner bearing an pivotally mounted on the outer surface of switch column 27. Reference numeral .33 has been applied to generally indicate the pivotablc unit including parts 30.31.32.34.35.36..

As clearly shownin FIG. 2 the fixed reversing switch con tact; and are pr vi ed with terminals or c nnectors 37 for formerwinding.

I The above described selector switch and reversing switch structure is topped by a drive 40 for the same. Drive 40 is arranged in a drive housing 39. Reference numeral 41 has been applied to indicate a crank mounted on rotatable shaft 41, intended to be operated by motor means not shown by the intermediary of spur gear 49 mounted on shaft 50 meshing with spur gear 48 mounted on shaft 41'. Crank 41 operates a pair of geneva gears 42,43 of which one 42 is arranged above crank 41 and the other 43 is arranged below crank 41. Crank 41 includes a pair of cams or pins angularly displaced 180 deg. intended to engage geneva gears 42,43. Geneva gear 42 is provided to operate contact bridges 23 and geneva gear 43 is provided to operate contact bridges 24. To this end contact bridges 23 are tied to geneva gear 42 and contact bridges 24 are tied to geneva gear 43 by tie means as will be explained below.

Geneva gears 42.43 are provided with substantially radially extending slots or recesses 44,45. FIG. 7 shows the recesses 44,45 in geneva gear 43, and geneva gear 42 is provided with like substantially radially extending recesses or slots. It will be apparent from FIG. 7 that slots or recesses 44 are outwardly flaring and that slots or recesses 45 have substantially the same width along their entire length, except at their closed ends. The relatively large or outwardly flaring slots or recesses of geneva gears 42, 43 result in relatively small angular displacements when these gears are engaged by the pins of crank 41 and pivoted. On the other hand, the relatively narrow slots or recesses 45 result in relatively large angular displacements when gears 42,43 are engaged by the pins of crank 41 and pivoted.

It will be apparent from FIG. 7 that the lower geneva gear 43 is provided with a drive pin 46 engaging upon each complete revolution of gear 43 the fork-shaped end 48 of a one sided reversing lever 49 pivotable about shaft 41. The fork-shaped end 48 of reversing lever 49 is permanently engaged by drive pin 47 integral with pivotable unit 34, described above in detail. Drive pin 46 engages the forkshaped end of reversing lever 49 only at the end of each full revolution of geneva gear 43. As contact bridges 24 move away from fixed contacts 12 into engagement with contacts K, reversing switch contacts-30 are pivoted out of engagement with fixed reversing switch contacts and into engagement with fixed reversing switch contacts The latter position has been shown in FIG. 2. The aforementioned pivotal motion of movable reversing switch contacts 30 is effected by the pivotal motion of reversing lever 49 transmitted by drive pin 47 to pivotable unit 34 including the vertical insulating bars 32.

The following is a description of the mechanism for transmitting the pivotal motions of geneva gears 42,43 to contact bridges 23,24. Geneva gear 42 is provided with an axial projection 42' integral with an annular member 42" mounted on, and pivotable around, column 27. The upper end of a tie rod 38,0f insulating material is affixed to annular member 42" and the lower end of said tie rod 38 is affixed to contact bridges 23 so that contact bridges 23 are driven in unison with geneva gear 42. In FIG. I tie rods 38 are broken away at a point close to annular member 42" and thus FIG. i does not show the mechanical connection between tie rod 38 affixed to annular member 42" and contact bridges 23. The aforementioned axial projection 42' of geneva gear 42 projects transversely across geneva gear 43 which is provided with a sector-shaped slot for the passage of projection 42'. The length of this slot is sufflcient to allowunimpeded pivotal movements of geneva gear 42. Geneva gear 43 is provided with a hub member 43 having an axial projection 43" integral with an insulating rod 38 projecting verticallyin downward direction to which con-.

tact bridges 24 are attixed. In FIG. I the tie rod 38 integral with projection 43" is broken away at a point immediately adjacent axial projection 43". and thus the points where the aforementioned tie rod 38 is affixed to contact bridges 24 is not shown in FIG. 1. FIG. 1 shows the lower ends of both tie rods 38 of insulating material. As shown in FIG. 1 the lower ends of tie rods 38 are integral with two annular members 42" and 43". respectively. of which each is pivotable about column 27 and of which each is in the shape of a bearing. The upper annular bearing 36 for the pivotable contact structure 33'including Contacts 39 forms sector-shaped apertures for the transverse passage of parts 32 and 43 through it.

FIG. 4 is a diagrammatic representation of the circuitry of 5 I the structure of FIG. 1. A transformer'includes a nontapped winding Tr-having a terminal P permanently conductively connected by lead L tofixed contact K and a tapped winding Tr having 13 taps numbered from 1 to 13 and ends All even selector switch taps numbered 2-12 are connected to contacts 2-12 arranged in a circular pattern, and all odd selector switch taps numbered 1-13 are conductively connected to contacts l-l3jarranged in another circular pattern. Tap 1 is conductively connected to fixed switch contact 1, tap 2 is conductively connected to fixed switch contact 2, etc., and tap 13 is conductively connected to fixed switch contact 13. Such an arrangement of leads interconnecting corresponding taps of a tapped windingand fixed contacts of a selector switch has been illustrated in FIG. 4 of US. Pat. No. 3,176,089 to A. Bleibtreu' et al., Mar. 30, 1965 for Load TapChangers for Transformers but has been shown only diagrammatically in FIG. 4 where the plurality of leads from the various taps 1-13 to the various fixed contacts 1-13 of the switch have been indicated by a single line. in H0. 4 the ends of the tapped windings are indicated by reference characters and The ends t, of the tapped windings Tr of each phase U,V,W are supposed to be conductivelyconnected to a fixed reversing switch contact and to a fixed reversing switch contact which has, been diagrammatically indicated in FIG. 4. 1n Fit];

4 reference numeral 23 has been applied to indicate the pivotable contact arm or contact bridge adapted to selectively connect either of the odd numbered fixed contacts 1-13 to the slip ring 25 and reference numeral 24 has been applied to indicate the pivotable contact arm or contact bridge adapted to selectively connect either of the even numbered fixed con;

tacts 2-12 and fixed cont act K to the fixed slip ring 26 it will be apparent from the foregoing that the voltage of nontapped winding Tr is boosted'when contact bridges 23, 24 engage any of fixed contacts 1-13 and contacts 30 interconnect conductively contacts+ and K, and that the voltage of nontapped winding Tr is bucked when contact bridges 23,24 engage any of fixed contacts 1-13 and contacts 30 interconnect conductively contacts K and Slip rings 23,24 are connected to leads L',l for connecting the same in a conventional fashion to a transfer switch and its switchover resistors as shown, for instance, in the above U.S. Pat. No. 3,176,089.

As shown in FIG. 5 fixed contacts K are in the form of rods and the radially outer ends of contact bridges 24 are formed by a pair of'fingers engaging both the upper and the lower side of the rod-shaped contacts K. Contacts K project transversely through vertical insulating bars 21 by which they are supported. The pivotable contact segments 30 engage both sides of rod-shaped contacts K and are biased by spring action into engagement with rod-shaped contacts K. Each contact segment 30 is arranged inside of a segment-shaped support 31 therefor. The right ends of rod contacts K are screw-threaded to secure to them terminals such as terminal 51 shown in FIGS. 1-3. Mounted on rod contacts K are two clamping members each to one side of insulating bar 21 for securing the former to the latter.

As shownin FIG. 1 the upper end of column 27 may be in the'form of a plate forming a bearing 27 As shown in FIGS. 6 and '7 the upper end of column 27 may be of reduced diameter and may be in the form of a vertical shaft 27" for mounting parts 34,43 and d2 thereon.

We claim as our invention:

1. A combined selector switch and reversing switch for use in tap-changing regulating transformers, said switch including:

a. a first plurality of fixed contacts (1,3,5...9,11,13) arranged to form a first circular pattern, the constituent contacts (l,3,5...9,11,il3) of said first circular pattern having a relatively small circular pitch (a) at oneside of for supporting shaft said pattern and a relatively large circular pitch (6) at the opposite side of said pattern;

. a first contact arm (23) pivotable about the center of said first circular pattern and having a radially outer end selectively engageable with each of said first plurality of fixed contacts (1,3,5 ,7,9,l1,13);

c. a second plurality of fixed contacts (2,4,6...l0,12,l() arranged to form a second circular pattern in coaxial relation to said first circular pattern, the constituent contacts (2,4,6...10,12,K) of said second circular pattern having a relatively smallcircular pitch (a) at one side of said pattern and a relatively large circular pitch (3) at the opposite side of said pattern, the region of said second circular pattern where there is a relatively large circular pitch (B) between the constituent contacts (2,4,6...10,l2,K) thereof including a center contact (K);

. a pair of additional fixed contacts immediately adjacent said center contact (K) each having the same circular pitch relative to said center contact (K) and each forming a part of said second circular pattern;

e. a second contact arm (26) pivotable about the center of said second circular pattern and having a radially outer end selectively engageable with each of said second plurality of fixed contacts (2,4,6...10,12,K); and

a movable reversing contact (30) pivotable about the center of said second circular pattern for selectively conductively connecting said center contact (K) with one of said pair of additional fixed contacts .2. A combined selector switch' and reversing switch as specified in claim 1 including:

a. a column (27) arranged in the center of said first and second circular pattern of fixed contacts (1,3,5...9,1 1,1

3;-,2,4...12,+K) supporting a pair of slip rings (25 26),

one of said pair of slip rings (25) being engaged by said first contact arm (23) and the other of said pair of slip rings (26) being engaged by said second contact arm (24); and

b. arm means (34,35) extending radially outward from said column (27) each having a radially inner end defining a bearing (36) engaging the outer surface of said column (27) and each having a radially outer end affixed to said movable reversing contact (30) to operate said movable reversing contact. I

3. A combined selector switch and reversing switch as specified in claim 1 wherein the constituent contacts of said first circular pattern of fixed contacts (1,3,5...9,ll,13) and the constituent contacts of said second circular pattern of fixed contacts (-,2,4...l2,+,K) are supported by a squirrel cage structure formed by a plurality of vertical insulating bars (21) defining a cylindrical surface, wherein said center contact (K) projects transversely through one of said plurality of bars (21) to the outside of said squirrel cage structure, and wherein said movable reversing contact (30) is arcuate in shape, arranged outside said squirrel cage structure in coaxial relation to said second circular pattern and engaged by a radially outer portion of said center contact (K).

4. A polyphase combined selector switch and switch including:

a. a plurality of vertical insulating bars (21) in a cylindrical pattern and forming a squirrel-cage insulating structure;

b. a plurality of superimposed layers (U,,U,,V,,V ,W,,W,)

' of fixed contacts supported by the constituent bars (21) of said squirrel-cage structure, alternate of said layers reversing (Q V W;) including a center contact (K )and a pair-2f selectively conductivelfc'onnecting said center contact (K) with one of said pair of immediately adjacent contacts of said alternate of said layers (U ,V ,W,).

5. A polyphase combined selector switch and reversing switch as specified in claim 4 including: 5 a. a column (27) arranged in the center of said squirrel-cage insulating structure supporting a plurality of slip rings (25,26) .each engaged by the radially inner end of one of said plurality of contact arms (23,24);

b. a pair of operating arms (34,35) for said plurality of reversing contacts (30), said pair of operating an'ns (34,35) each defining a bearing (36) at the radially inner end thereof engaging the outer surface of said column (27), one of said pair of operating arms (34) being arranged adjacent the upper end of said column (27) and the other of said pair of operating arms (35) being arranged adjacent the lower end of said column (27 and the radiallyouter ends of said pair of operating arms (34,35) being being arranged adjacent the lower end of said column together by vertical insulating bars (32) for joint movement of said pair of operating arms (34,35).

6. A polyphase combined selector switch and reversing switch as specified in claim'5 wherein a gear drive (40) for said plurality of contact arms (23,24) and for said pair of operating arms (34,35) is arranged above said squirrel-cage structure and wherein a pin (49) projects upward from said one of said pair of operating arms (34) into engagement with said gear drive (40).

7. A polyphase combined selector switch and reversing switch as specified in claim 5 wherein said gear drive (40) includes a crank mechanism (41); a pair of geneva gears (42,43) operated by said crank mechanism (41) for operating said plurality of contact arms (23,24); a reversing contact operating lever (49) pivotable about a fixed point (41) and having a fork-shaped end (48) engageable by a pin (46) integral with one of said pair of geneva gears (43), said forkshaped end (48) of said reversing contact operating lever (49) being permanently engaged by said pin (47) projecting upward from said one (34) of said pair of operating arms (34,35). 

1. A combined selector switch and reversing switch for use in tap-changing regulating transformers, said switch including: a. a first plurality of fixed contacts (1,3,5...9,11,13) arranged to form a first circular pattern, the constituent contacts (1,3,5...9,11,13) of said first circular pattern having a relatively small circular pitch ( Alpha ) at one side of said pattern and a relatively large circular pitch ( Beta ) at the opposite side of said pattern; b. a first contact arm (23) pivotable about the center of said first circular pattern and having a radially outer end selectively engageable with each of said first plurality of fixed contacts (1,3,5,7,9,11,13); c. a second plurality of fixed contacts (2,4,6...10,12,K) arranged to form a second circular pattern in coaxial relation to said first circular pattern, the constituent contacts (2,4,6...10,12,K) of said second circular pattern having a relatively small circular pitch ( Alpha ) at one side of said pattern and a relatively large circular pitch ( Beta ) at the opposite side of said pattern, the region of said second circular pattern where there is a relatively large circular pitch ( Beta ) between the constituent contacts (2,4,6...10,12,K) thereof including a center contact (K); d. a pair of additional fixed contacts (+,-) immediately adjacent said center contact (K) each having the same circular pitch relative to said center contact (K) and each forming a part of said second circular pattern; e. a second contact arm (26) pivotable about the center of said second circular pattern and having a radially outer end selectivEly engageable with each of said second plurality of fixed contacts (2,4,6...10,12,K); and f. a movable reversing contact (30) pivotable about the center of said second circular pattern for selectively conductively connecting said center contact (K) with one of said pair of additional fixed contacts (+,-).
 2. A combined selector switch and reversing switch as specified in claim 1 including: a. a column (27) arranged in the center of said first and second circular pattern of fixed contacts (1,3,5...9,11,13;-,2,4...12, +,K) supporting a pair of slip rings (25,26), one of said pair of slip rings (25) being engaged by said first contact arm (23) and the other of said pair of slip rings (26) being engaged by said second contact arm (24); and b. arm means (34,35) extending radially outward from said column (27) each having a radially inner end defining a bearing (36) engaging the outer surface of said column (27) and each having a radially outer end affixed to said movable reversing contact (30) to operate said movable reversing contact.
 3. A combined selector switch and reversing switch as specified in claim 1 wherein the constituent contacts of said first circular pattern of fixed contacts (1,3,5...9,11,13) and the constituent contacts of said second circular pattern of fixed contacts (-,2,4...12,+,K) are supported by a squirrel cage structure formed by a plurality of vertical insulating bars (21) defining a cylindrical surface, wherein said center contact (K) projects transversely through one of said plurality of bars (21) to the outside of said squirrel cage structure, and wherein said movable reversing contact (30) is arcuate in shape, arranged outside said squirrel cage structure in coaxial relation to said second circular pattern and engaged by a radially outer portion of said center contact (K).
 4. A polyphase combined selector switch and reversing switch including: a. a plurality of vertical insulating bars (21) in a cylindrical pattern and forming a squirrel-cage insulating structure; b. a plurality of superimposed layers (U1,U2,V1,V2,W1,W2) of fixed contacts supported by the constituent bars (21) of said squirrel-cage structure, alternate of said layers (U2,V2,W2) including a center contact (K) and a pair of immediately adjacent contacts (+,-); c. a plurality of contact arms (23,24) each arranged in one of said layers (U1,U2,V1,V2,W1,W2) each pivotable about the axis of said squirrel-cage structure and each having a radially outer end selectively engageable with the constituent contacts of said layers (U1,U2,V1,V2,W1,W2); d. a plurality of movable reversing contacts (30) pivotable about the axis of said squirrel-cage structure each arranged in said alternate of said layers (U2,V2,W2) for selectively conductively connecting said center contact (K) with one of said pair of immediately adjacent contacts (+,-) of said alternate of said layers (U2,V2,W2).
 5. A polyphase combined selector switch and reversing switch as specified in claim 4 including: a. a column (27) arranged in the center of said squirrel-cage insulating structure supporting a plurality of slip rings (25, 26) each engaged by the radially inner end of one of said plurality of contact arms (23,24); b. a pair of operating arms (34,35) for said plurality of reversing contacts (30), said pair of operating arms (34,35) each defining a bearing (36) at the radially inner end thereof engaging the outer surface of said column (27), one of said pair of operating arms (34) being arranged adjacent the upper end of said column (27) and the other of said pair of operating arms (35) being arranged adjacent the lower end of said column (27), and the radially outer ends of said pair of operating arms (34,35) being tied together by veRtical insulating bars (32) for joint movement of said pair of operating arms (34,35).
 6. A polyphase combined selector switch and reversing switch as specified in claim 5 wherein a gear drive (40) for said plurality of contact arms (23,24) and for said pair of operating arms (34,35) is arranged above said squirrel-cage structure and wherein a pin (49) projects upward from said one of said pair of operating arms (34) into engagement with said gear drive (40).
 7. A polyphase combined selector switch and reversing switch as specified in claim 5 wherein said gear drive (40) includes a crank mechanism (41); a pair of geneva gears (42,43) operated by said crank mechanism (41) for operating said plurality of contact arms (23,24); a reversing contact operating lever (49) pivotable about a fixed point (41'') and having a fork-shaped end (48) engageable by a pin (46) integral with one of said pair of geneva gears (43), said fork-shaped end (48) of said reversing contact operating lever (49) being permanently engaged by said pin (47) projecting upward from said one (34) of said pair of operating arms (34,35). 